The present invention generally relates to information display systems, and more particularly to an improved method for bypassing user irrelevant screen updates in a system environment which implements IBM 3270 display system type of protocols between a host application and the display.
System guided dialogues using menu selection are commonly used in many data and word processing systems. Menu selection systems provide a means of selecting operations and retrieving information which reduces operator training requirements and the need for the operator to memorize complex command sequences. However, the necessity to sequentially cycle through a system-ordered set of user unneeded menu displays or other displays can be time consuming and can contribute to operator boredom as the operator gains experience.
Bypassing user unneeded but system dictated screen displays is particularly desirable in certain types of systems, such as the IBM 3270 information display system, where there may be a significant amount of time required for communication between a host application and a display terminal. In this type of system the display terminal or personal computer communicates with a host processor application program via a display controller. Systems of IBM 3270 information display type use a half-duplex session protocol between the display and the host application. This half-duplex protocol is implemented in different ways depending on whether a terminal is: a) attached to a controller which is channel attached to the host processor; b) attached to a controller which is connected to a communication controller using synchronous data link control protocols; or c) attached to a controller which is connected to a communication controller using binary synchronous communication protocols. In all cases the terminal requires permission of the host application to transmit data while the host application is free to transmit data to the display or read data from the display at any time. After a transmission from the display terminal to the host application, system protocols lock the terminal from a further transmission until the application can decide on an action and that action is transmitted back to the display.
The host application assumes that the last screen it transmits is currently displayed except for user modifications. IBM 3270 display system protocols and terms used herein are more fully described in "IBM Information Display System Data Stream Programmers Reference," IBM Publication No. GA23-0059-0. It will be appreciated that in a system which uses such protocols, in certain situations, ambiguous data may result if the keyboard were unlocked and data screens were aborted. For example, in a sequence of host commands: erase write; write; read buffer; if the original erase write were to sets fields not altered by the write, the read buffer command would read incorrect fields if the original erase write were aborted.